Bulky, high-strength polyethylene terephthalate yarns



United States Patent 3,371,475 BULKY, HIGH-STRENGTH POLYETHYLENE TEREPHTHALATE YARNS Adly Abdel-Moniem Gorrafa, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Sept. 20, 1965, Ser. No. 488,788 4 Claims. (Cl. 57140) ABSTRACT OF THE DISCLOSURE A spun yarn of polyethylene terephthalate having a twist multiplier of from 1.4 to 2.0 and consisting of textile fibers of less than 2.0 denier per filament having measured staple lengths of from 2.25 to 3.0 inches. Blends of polyethylene terephthalate with minor portions of rayon and with minor portions of cotton are also disclosed. The yarn possesses high 'bulk 'and covering power with a good degree of strength.

This invention relates to textile yarns spun from staple, and more particularly to polyethylene terephthalate textile yarns which possess 'high strength and which impart to fabrics woven therefrom a high degree of covering power.

It is known that structural changes in yarn produce consequent effects on the quality of the yarn; for example, lowering the twist multiplier produces looser and bulkier yarn. It is also known, however, that such adjustment of yarn structure produces a consequent effect on other quality attributes; for example, lowering the twist multiplier produces lower yarn strength assuming, of course, that the initial twist of the yarn was at such a level 'as to produce optimum yarn strength. The practical employment of these known concepts which produce contradictory effects on yarn quality attributes has led to what was heretofore known as optimum structural combinations, the adjustment of which was dictated by the particular use contemplated for the yarn. Thus, if a highbulk yarn w'as contemplated the twist would be lower and strength would be sacrificed and vice versa.

Attempts to obviate these contradictory effects produced by yarn structural adjustment so that bulk would not be sacrificed for strength would lead to consideration of staple length and fiber denier. However, the cotton system of staple processing is limited in its use to shorter staple lengths and the worsted system, although being able to process longer lengths, is not compatible with the lower deniers. Furthermore, the effect of pilling in fabrics, which is known to occur in fabrics composed of strong, fine-denier fibers, and lower twist yarns brought about a reluctance to experiment, and hence an acquiescence in the above-mentioned optimum combinations.

This invention provides a bulky, high-strength polyethylene terephthalate textile y'arn, the quality attributes of which are obtained by a heretofore unknown combination of structural parameters. Another provision is polyethylene terephthalate textile yarn, the structural parameters of which are so designed that yarn strength is not sacrificed for bulk, 'and vice versa. A further provision is a textile yarn which may be spun from staplelength fibers on conventional processing equipment, and which imparts to fabrics woven therefrom an outstanding degree of cover, high-strength and pleasing aesthetic qualities.

These provisions are realized by polyethylene terephthalate textile yarn having a twist multiplier value of 1.4 to 2.0 and consisting of textile fibers of less than 2.0 denier per filament having a measured staple length of 2.25 to 3.0 inches (57.1 to 76 mm.). The term polyethice ylene terephthalate yarn comprehends yarns consisting of polyethylene terephthalate fibers and yarns consisting of blends with other textile fibers wherein the polyethylene terephthalate fibers 'are the major component, e.g., including the common textile fiber blend of 65% by weight polyethylene terephthalate fibers with 35% rayon fibers. It has also been found that blends with cotton fibers, of the usual inch to about 1 /2 inches staple length, may be used to attain the desirable attributes of this invention, e. g., blends of up to about 20% by Weight of cotton fibers with about or more of textile fibers of less than 2.0 denier per filament and having a measured staple length of 2.25 to 3.0 inches. The textile fibers are preferably about 1.5 denier per filament and not less than 0.6 denier per filament.

The term twist multiplier as used herein designates the numerical value of the turns-per-inch of the yarn divided by the square root of the cotton count of the yarn. It should be noted that twist multiplier as used herein is based on the English Cotton Count System.

In the present specification two terms are used to describe the staple length of the fibers; measured staple length and cut staple length. The measured staple length is measured in accordance with ASTM Procedure D1440-55, for determination of the upper quartile value (U.Q.L.) for samples of fibers having a length distribution within the limits of good drafting ability in conventional cotton system processing. The term cut staple length refers to the staple cutting machine setting at which the continuous filaments, e.g., tow, are cut. Accordingly, in the present specification when it is said that the fibers are cut to a certain length the cut staple length is meant. Many staple cutting machines cut tow to staple while the tow is under tension, therefore, at 'a specific cut staple length setting the measured staple length of the resulting staple will vary inversely with the amount of tension which was applied to the tow during the cutting operation. For example, if staple is produce by introducing tow to a staple cutting machine, the machine having 2.5 inches cut staple length setting, the tow being under little tension, the measured st'aple length of the resulting staple will be approximately 2.45 inches, While if the tow is under a greater tension while being cut to staple by the same machine set at the same cut staple length setting, the measured staple length of the resulting staple will be approximately 2.35 inches.

It has long been known that to raise the twist multiplier of a yarn, all other parameters remaining constant, yarn strength is increased due to the increased special compactness and the fact that the fibers are induced to move closer to each other and thus the fiber-to-fiber frictional forces are increased. The closer spacial relationship of fibers to each other inevitably produces lower yarn bulk. Conversely, if the twist multiplier is lowered the fibers are not as close to each other and thus frictional forces are reduced and yarn is weaker, but bulkier. Of course, an excessive increase in the twist multiplier of cottonsystem spun yarn above the twist multiplier which is normally used for textile purposes may also lower the yarn strength because of the increase in the helix angle of the fibers (obliquity) and the decreased fiber mobility which produces uneven yarn stress distribution.

It has now unexpectedly been found that if the measured staple length is from 2.25 to 3.0 inches (57.1 to 76 mm.) and the fiber denier is less than 2.0 (preferably about 1.5), the normal yarn twist multiplier of 3.5 to 4.0 can be drastically reduced to a value below 2.0 to produce bulky polyethylene terephthalate yarn which maintains a surprisingly high degree of strength. In fact, the strength of the yarn so produced is equivalent to, and may be greater than, the strength of yarn produced by cotton system processing from the conventional 1.5 inch (38 mm.) staple with the conventional 3.5 to 4.0 twist multiplier. This discovery is unexpected from prior-art teaching that the strength is seriously decreased by lowuseful for shirting, sheeting, dress-wear, and home furnishings.

In finishing fabrics containing the yarns of this invention it will be found that calendaring will transform ering the twist multiplier to about 2.75 to 3.0 on the 5 the high bulk property into high covering-power in the cotton system. Within the limitations herein set forth, fabric. Finishing operatons used are those common in the bulky yarn may be produced at the lower twist rnulthe art. tiplier and no consequent decrease in yarn strength is Surprisingly, the fabrics produced from this yarn produced thereby. The twist multiplier of the yarn of can perform satisfactorily in actual use without risk of the present invention is 1.4 to 2.0, and preferably from pill development in spite of the extremely low twist 1.65 to 1.85. multiplier and fine denier ranges specified.

The choice of staple length for the yarn of this in- The invention is further illustrated by the following vention is important in that if the length is too long, examples without being restricted thereto. while the denier per filament is less than 2.0, the staple EXAMPLE I will not process well in carding and results in increased nepping. The operative range of the measured staple This example illustrates that decreased twist multiplier length for the yarn of this invention is 2,25 to 3,0 according to the specification set forth hereinabove does inches (57.1 to 76 mm.). Preferably, the measured not adversely affect yarn strength. It further shows that staple length of the fibers or blend of fibers of the yarn increase in staple length is not the only factor that leads of this invention is 2.25 to 2.5 inches (57.1 to 63.5 mm.) t0 improved y Strengthand the length variation of the individual fibers is within Polyethylene terephthalate is spun to produce a semithe limits of good drafting ability for conventional cotton dull continuous filament yarn of 15.5 relative viscosity system processing. It is to be understood that the yarns d 1.5 d nier p r filament. This yarn is divided into of the present invention may contain minor proportions three portions- The first Portion is Cut to inch of fibers of measured staple length less than 2.25 inches, staple and second is cut to 2.5 inch (63.5 mm.) staple and providing that the measured staple length of the blend, the third is cut to 3 inch (76 mm.) staple by standard as a whole, is within the above-established limitations. methods of staple manufacture. The measured staple Fibers which can be used for this invention are numlength of these portions are 1.50, 2.34, 3.01 inches (38, erous. In general, any synthetic, man-made or natural 59.5, 76.4 mm), respectively. Each portion is further textile fiber can be used provided its length and fineness divided into two subportions. The first subportion is characteristics conform to the specifications established spun to a yarn of 30/1 cc. (19.7 Tex) by conventional herein. Polyethylene terephthalate fibers and blends spinning methods and the second su-bportion is spun to thereof with other fibers are preferred. a yarn of 50/1 cc. (11.8 Tex) by the same methods.

Preferably, the cotton system or modified cotton system Each of these yarns is given a certain twist multiplier as of staple processing is used in the practice of the present shown in the following table which also shows the physiinvention. In general, the carding operation should be cal properties of these yarns.

TAB LE I 30/1 cc. (19.7 Tex) Yarns from 1.5 inch (38 mm.) Cut Staple Length 30/1 cc. (19.7 Tex) Yarns from 2.5 inch (63.5 mm.) "Cut Staple Length x) Yarns from 3.0 inch (76 mm.)

30/1 cc. (19.7 Te

Cut Staple Length Twist Lea C.V. Twist Lea C.V. Twist Lea C.V. multiplier Product percent multiplier Product percent multiplier Product percent 50/1 cc. (11.8 Tex) Yarns from 1.5 inch (38 mm.) Cut Staple Length 50/1 cc. (11.8 Tex) Yarns from 2.5 inch (63.5 mm.) Cut Staple Length 50/1 cc. (11. 8 Tex) Yarns from 3.0 inch (76 mm.) Cut Staple Length Twist Lea C.V. Twist Lea C.V. Twist Lea C.V. multiplier Product percent multiplier Product percent multiplier Product percent properly adjusted to avoid nep formation to an objec- Lea Product, as used herein, is the numerical value obtionable degree. Subsequent drafting operations are easily accomplished by conventional practices with the exception of obvious machine adjustments (e.g., roller setting) compatible with the staple length, and length distribution of the fiber stock being processed. In the roving step, if any, a twist multiplier significantly lower than usual will be found conducive to better drafting performance in the spinning operaton. The spun yarn count can vary from a very coarse 4/1 cc. (147.6 Tex), to a very fine 100/1 cc. (5.9 Tex), bearing in mind that yarn uniformity at the fine counts should be within the conventionally acceptable limits.

Yarn produced in accordance with the present invention can be used to make fabrics of plain, twill, satin, sateen, oxford, basket and like weaves. Such fabrics are tained by multiplying the cotton count of the yarn by the Skein Breaking Strength in pounds. The Skein Breaking Strength is measured on a skein prepared by winding yards (109.7 meters) of yarn around a reel of 1.5-yard (1.37 meter) circumference, placing the skein on a hook, and applying a load to the bottom of the skein. The load is increased until the skein breaks and the value of the load in pounds is recorded as the Skein Breaking Strength.

C.V. percent (coefiicient of variation), as used herein, is a measure of the variation of thick and thin segments in a yarn integrated over a specific length of the yarn. Commercially available uniformity testers may be used.

Relative viscosity (R.V.) pertains to the ratio of the viscosity of a 10% solution of the polymer in a mixture of parts of phenol and 7 parts of 2,4,6-trichlorophenol (by weight) to the viscosity of the phenol/trichlorophenol mixture, per se, measured in the same units at C.

EXAMPLE II semidull polyethylene terephthalate of 15.5 R.V., 1.5 denier per filament and 2.5 inches (63.5 mm.) cut staple length and 35% viscose rayon of 1.5 denier per filament and 2.5 inches (63.5 mm.) cut staple length. This blend is divided into two portions. The first portion is spun to 50/ 1 cc. (11.8 Tex) and given a twist multiplier of 1.65 in the Z direction; the second is spun to /1 cc. (17.7 Tex) and given a twist multiplier of 1.45 Z. The yarns are woven into fabrics of the description shown in Table III and each fabric is finished by the sequence of padding, desizing, crabbing six passes in the crab, scouring and bleaching, drying, singeing, calendering, heat setting, light scouring with the addition of a softener, drying and semidecating. The construction and characteristics of these finished fabrics are shown in Table III.

TABLE III Cut Twist Loom Finished Fabric Filling Air Yarn Count Staple Multi construc- Construc- Weight Strength, Perme- Ir It Length plier, tion (warp tion oz./sq. lb./elong. ability Item Fabrlc Warp Filling (Inches) and fill) yard Percent Ilg A"-- Control 50/1 cc. (11.8 Tex) 50/1 cc. (11.8 Tex) 1. 5 3. 50/ /3. 50 100 x 2 114 x 75 2 91 37. 7/27 101 74. 1 4. 0 B-- Test 50/1 cc. (11.8 Tex) 50/1 cc. (11.8 TeX) 2. 5 1. 65/ /1. 65 90 X 72 107 X 77 2. 70 32. 9/29 27 77. 1 1. 8 C-- Control 50/1 cc. (11.8 Tex) 30/1 cc. (19.7 Tax)" 1 5 3. 50/ I3. 50 100 x 60 111 x 64 3. 40 57/27 97 77. 1 3. 5 D"-- Test 50/1 cc. (11.8 Tex)--- 30/1 cc. (19.7 Tex)-- 2 5 1. 65/ /1. 45 90 X 60 107 x 66 3. 16 55/31 21 80. 5 1. 43

tions are 1.50 and 2.34 inches (38 and 59.5 mm.) respectively. Viscose rayon fiber of 1.5 denier per filament is produced and divided into two portions. The first is cut to 1.5 inch (38 mm.) staple and the second to 2.5 inch (63.5 mm.) staple. The measured staple length of these portions are 1.50 and 2.56 inches (38 and 65.0 mm.) respectively. A staple blend is then prepared consisting of 65% polyethylene terephthalate 1.5 inch (38 mm.) staple and 1.5 inch (38 mm.) rayon. The 2.5 inch (63.5 mm.) polyethylene terephthalate staple is then blended with the 2.5 inch (63.5 mm.) rayon staple to a proportion of 65% polyethylene terephthalate to 35% rayon. Yarn is then spun from these two staple blends by spinning at different twist multipliers as shown in the following table which also shows the properties of the yarns obtained thereby.

where RC is reflectance of a white plate covered with fabric; RC is reflectance of a black plate covered with fabric; R is reflectance of an uncovered white plate; R

is reflectance of an uncovered black plate. Reflectance is TABLE II Cotton Count Cut Staple Length Twist Lea C.V.

Mult' lier Product Percent 30/1 cc. 1.5 inches (38 mm.) 3. 50 2,850 15. 4 30/1 cc. 2.5 inches (63.5 mm.) H 1. 3, 040 13.0 30/1 cc. 7 Tex) do 1. 49 3, 550 15. 3 30/1 cc. 7 Tex) do 1.80 3, 280 13. 0 40/1 cc. 1.5 inches (38 mm.) 3. 50 2, 550 15. 7 40/1 cc. 2.5 inches (63.5 mm 1. 70 2, 740 16. 1 50/1 cc. 1.5 inches (38 mm.) 3.50 2, 260 19. 0 50/1 cc. 2.5 inches (63.5 mm.) 1. 47 2, 350 18. 5 50/1 cc. Tex) do 1. 2, 770 17. 6 50/1 cc. Tex) .d0 1. 83 2, 770

EXAMPLE III This example shows the improved fabric covering power obtained in fabric Woven from the yarns of the present invention as compared to fabric woven from yarns of the prior art.

Four fabrics are prepared from yarns of the following description:

To cont rol yarns are prepared from a blend of 65% semidull polyethylene terephthalate of 15.5 R.V., 1.5 denier per filament and 1.5 inch (38 mm.) cut staple length and 35 viscose rayon of 1.5 denier per filament and 1.5 inch (38 mm.) cut staple length. This blend is divided into two portions; the first portion is spun to 50/1 cc. (11.8 Tex) and given a twist multiplier of 3.5 and the second portion is spun to 30/ 1 cc. (19.7 TeX) and given a twist multiplier of 3.5. i

Two test yarns are prepared from a blend of 65% measured by using a photoelectric reflection meter Model No. 610 manufactured by Photovolt Corp., of New York. White and black plates used are Photovolt Catalog No. 6162 and No. 6163. A green tri-stimulus filter is used, and the light intensity reflected from the fabric and/or the plate at a 45 angle from the plane of the plate is measured.

It is a measurement of light transmission through a fabric. A Durst No. 609 Projector manufactured by Durst S.A., Italy, is used as the light source and diffusing element. Light from the projector is cast upon a fabric sample and the amount of light transmitted through the fabric is measured by a Photo Multiplier Microphotometer, Cat. No. 10-211, manufactured by American Instrumerit Co., Inc. of Maryland. The reading of the microphotometer with the fabric sample in the apparatus is recorded as percentage points of the original amount of 7 8 light with no fabric sample in the apparatus. This perhours and machine-washed 15 times. The pilling rating centage light transmission is recorded as I of the shirts of the test fabric averages 4.75.

Dress shirts are tailored from the test fabric of Ex- EXAMPLE IV ample III, the structure of which is designated as Item B of Table III with the exception that the loom construc- This example shows that, contrary to what would be tion is 90 X 60 (about 35 eHdS/Cm- X 4 P The predicted b prior art teachings, fabrics f h present shirts are wear-tested and evaluated in the same manner invention do not pill severely and perform as well in this as The shifts of the first test fabric of this P The respect a nt ol f b i f h prior t pilling rating of the shirts after wear-testing averages 4.9.

A control yarn is prepared by normally processing a fiber blend consisting of 65% polyethylene terepthalate EXAMPLE VI staple, of 1.5 inch (38 mm.) cut staple length and 1.5 denier per filament, and 35% viscose rayon of L5 (38 Th1s example illustrates that yarns produced in accordmm) Staple length and L5 denier per filament ance with the present specification, which contain a mmor- A 50/1 m (1L8 Tex) yarn is spun from this blend at a ity of short staple-fibers, possess all the desirable attributes 3.5 twist multiplier. A control fabric is woven from this harem descnbedyam at 100 X 72 (39 ends/cm X 78 picks/cm) 100m Polyethylene terephthalate 1.5 denier per filament yarn Construction is produced according to the procedure of Example 1 and A test yarn is prepared identical to the control "yarn into tWO portiOnS. The first portion is cut to of this example except that the cut staple length is Inch Staple d file Second t0 Inch 2.5 inch (63.5 mm.) and the twist multiplier is 1.84. staple These p n are then Separately P This test yarn is used for the filling of a test fabric, the essed to Produce Carded ShVeI from each 12- C m d warp yarn of hi h i h t l yam d ib d above cotton slivers are prepared from Texas cotton of about in the present example. The loom construction for this 1% inch length y methods Common i the fabric is 100 x 72 (39 ends/cm. x 28 picks/cm) art. A control yarn consisting of 80% of the polyethylene The control and the test fabrics are finished according p h la e inch p e and 20% of the to the finishing procedure described in Example III above. c ton is prepared by draw-frame blending of slivers, fol- Dress shirts are tailored from the control fabric and lowed y normal Pr ss ng steps. The control yarn is from the test fabric and each is wear-tested. The shirts spun to /1 cc. (1?.7 Tex) and 3.50 twist multiplier. made from the test fabric have a pilling rating after wear- 30 A test yarn consisting of 80% of the polyethylene tertesting of 4.7 to 5.0 while the shirts made from the conephthalate 2.5 inch (63.5 mm.) staple and 20% of the trol fabric have a pilling rating after wear-testing of 5.0. cotton is similarly spun to 30/ 1 cc. (19.7 Tex) and Wear-testing as used herein refers to a test of the fol- 1.72 twist multiplier. Strength and uniformity of the lowing procedure: The shirt made from the test fabric yarns of this example are shown in Table IV.

TABLE IV Fiber Blend Twist Lea C.V. Yarn (Percent by weight) Multiplier Product (Percent) Control... 80t1.5-inch polyethylene terephthal- 3.50 2,850 16.3

3 8. 20cotton. Test 80t2.5-ineh polyethyleneterephthal- 1.72 2,940 16.5

a B. 20-eotton.

of the present example is worn by a human being during normal daily activity for 10 hours in one day; on the following day the shirt made from the control fabric of the present example is worn by the same person during an essentially identical course of daily activity for 10 hours. Each shirt is machine-washed on the day it is not worn; this procedure continues, the shirt of the test fabric and the shirt of the control fabric being worn by the same person on alternate days and washed on the day it is not worn until each shirt is worn for 200 hours and machine-washed 20 times. Pilling performance is evaluated by visually examining the collar and cufI areas of the test and control shirts which have been wear-tested. The collar and the cuff areas are visually rated with reference to a scale of numerical values of 1.0 to 5.0, 1.0 being the numerical value of a severely pilled fabric and 5.0 being the numerical value of a fabric with essentially The yarns of the present invention have the advantage of retaining their strength and imparting to fabrics woven therefrom a considerably high degree of covering power by a unique and special combination of certain structural specifications which are in direct contradiction to the prior art teachings.

A further economic advantage of the yarns of the present invention lies in the fact that conventional equipment may be used throughout the manufacture. Thus, no new equipment and capital expenditure is necessitated to produce these yarns. A saving is further realized due to 0 the fact that extremely low twist is sufficient.

Fabrics may be woven from these yarns to be used for garments or other purposes. These fabrics are produced with considerable degree of covering power and have a pleasing hand, drape and other aesthetical quali- 5 ties.

no pills. Since many different embodiments of the invention EXAMPLE v may be made without departing from the spirit and scope This example further illustrates the performance-inthereof, it is to be understood that the invention is not wear of fabrics the warp and filling yarns of which are limited by the specific illustrations except to the extent prepared in accordance with the present invention. defined in the following claims.

Dress shirts are tailored from the test fabric of Ex- I claim: ample III the structure of which is designated as Item 1. A bulky polyethylene terephthalate textile yarn D of Table III. The shirts are wear-tested and evaluated which possesses high strength and imparts a high degree according to the procedure described in Example IV above of covering power to fabric woven therefrom, the yarn with the exception that the shirts are worn a total of 150 having a twist multiplier value of 1.4 to 2.0 and consisting of textile fibers of less than 2.0 denier per filament having a measured staple length of 2.25 to 3.0 inches.

2. Yarn as defined in claim 1 wherein the twist multiplier value is 1.65 to 1.85, the fibers are about 1.5 denier per filament and the measured staple length is 2.25 to 5 2.5 inches.

3. Yarn as defined in claim 1 wherein the textile fibers are a blend of 65% polyethylene terephthalate fibers with 35% rayon fibers.

4. A bulky textile yarn which possesses high strength and imparts a high degree of covering power to fabric woven therefrom, the yarn having a twist multiplier value of 1.4 to 2.0, consisting of a blend of up to about 20% by Weight of cotton fibers, of inch to about 1 /2 inch staple length, with at least about 80% by weight of polyethylene terephthalate textile fibers of less than 2.0 denier 10 per filament and having a measured staple length of 2.25 to 3.0 inches.

References Cited UNITED STATES PATENTS 2,897,042 7/1959 Heiks 57l40 X 3,044,250 7/ 1962 Hebeler 57l40 FOREIGN PATENTS 212,352 1/ 1958 Australia.

229,710 8/ 1960 Australia.

609,794 10/ 1948 Great Britain.

610,096 10/ 1948 Great Britain.

870,017 6/ 1961 Great Britain.

JOHN PETRAKES, Primary Examiner. 

